diff --git a/internal/handlers/collections.go b/internal/handlers/collections.go
index 3edd69c..c566cd1 100644
--- a/internal/handlers/collections.go
+++ b/internal/handlers/collections.go
@@ -827,6 +827,11 @@ func (h *CollectionHandler) HandleBulkAddBooks(c echo.Context) error {
 }
 
 func (h *CollectionHandler) PreviewCollection(c echo.Context) error {
+	user := c.Get("user")
+	if user == nil {
+		return c.JSON(http.StatusUnauthorized, map[string]string{"error": "unauthorized"})
+	}
+
 	var req struct {
 		LibraryID     string          `json:"library_id"`
 		Rules         []services.Rule `json:"rules"`